Liquids exist in the smallest temperature range, so
liquids are the least common state of matter . . .
Kinetic Theory Description of the Liquid State According to the kinetic theory, motion of liquid
particles can be described as . . .
Properties of Liquids and the Particles Model – define each property Properties of Fluids
Definite Volume
Fluidity
Relative High Density
Incompressible
Dissolving Ability
Ability to Diffuse
Surface Tension
Tendency to Evaporate and Boil
Tendency to Solidify
13.1 Questions
Why are liquids more dense than gases? Molecules are closer together so more molecules
in a given area Why are liquids harder to compress than gases?
Same as above – molecules are closer Why do liquids diffuse slower than gases?
Particles are not moving as fast as gases Can a liquid boil without increasing the
temperature? How? Yes – lower the atmospheric pressure
10.3 Solids
“Solid as a rock, “ is the description of solid – something that is hard, unyielding, with a definite shape and volume. Many things other than rocks are solids. In fact, solids are more common than liquids.
This diagram shows the particles of a gas, liquid and solid.
Kinetic-Theory Description of the Solid StateAccording to the kinetic theory, the motion of solid particles can be described as….
Lower kinetic energy, less motion, more packed particles, and higher intermolecular forces (IMF)
Properties of Solids and the Particle Model – define each property: Properties of Solids Definite shape and volume Non-fluid Definite melting point High Density Incompressible Slow Diffusion
Crystalline Solids
Classification of crystals by arrangement and shape
Crystal Lattice (define) - The total 3-D array of points that describe the arrangement of the particles – a collection of unit cells.
The smallest portion of the crystal lattice that reveals the 3-D pattern of the entire lattices is the unit cell.
Types of Crystals
Face-centered (ex. Cu, Ag, Au)
Hexogonal (like oranges in a grocery store); (ex. Zn)
Binding forces in crystals
Binding Force Lattice consists of Formed When / Binding Force
Ionic crystals(+) and (-) ion as
arranged in regular patterns
Group 1/2 metals combine with Group 7/8 nonmetals
Covalent network crystals
Lattice sites contain single atoms
Atoms bond to neighbors, extending through a network, large chains form
Metallic crystals
(+) ions of the metal surrounded by a cloud of valence electrons
Each e- and the (+) metallic ions attract electrostatically
Covalent molecular crystals
Covalently bonded molecules held through IMF
For nonpolar molecules, London Forces; For polar molecules, Dipole-Dipole.
“Amorphous,” comes from the Greek for “without a shape.” Unlike crystals, amorphous solids do not
have a regular, natural shape, but instead take on whatever shape imposed on them.
Particle arrangement is not uniform; they are arranged randomly, like particles of a liquid.
Examples of amorphous solids – glass used
in fiberoptics (optical fibers transmit telephone conversations by means of light waves.
Amorphous solids are prepared by rapid cooling of thin film materials. Molecular examples Crystalline vs. Amorphous
10.4 Changes of State
Possible Changes of State
Change of State Name Example
Solid -> Liquid melting ice -> water
Solid -> Gas sublimation dry ice -> CO2 gas
Liquid -> Solid freezing water to ice
Liquid -> Gas vaporization Br(l) -> Br(g)
Gas -> Liquid condensation water vapor -> water
Equilibrium
What does equilibrium mean? It is a dynamic condition in which two
opposing changes occur at equal rates in a closed system.
What is a closed system? H2O in an open beaker H2O in a closed beaker
When a liquid changes to a vapor, as in evaporation, it absorbs heat energy and can be shown as: Open system evaporation – liquid + heat vapor Closed system evaporation – liquid + heat vapor
When a vapor condenses, as in condensation, it gives off heat energy and can be shown as: And condensation – vapor liquid + heat
The liquid vapor equilibrium can be rewritten as: liquid + heat ↔ vapor “The double yields sign represents a reaction at
equilibrium”
Le Chatelier’s Principle
What is it? LeChatelier When a system at equilibrium is disturbed by
the application of stress, the system reacts to minimize the stress.
Is temperature an example of stress? Yes.
What happens when you increase the temperature of a system? Equ. shift from heat ↓ liquid + increased heat ---> ↑ vapor
Le Chatelier’s Principle
What happens when you decrease the temperature of a system? ↓ vapor ---> ↑ liquid + decreased heat
What factor is controlling the decrease and increase of vapor and liquid? the temperature (heat)
Equilibrium Vapor Pressure of a Liquid
What is it? At equilibrium, the molecules of a vapor exert
a specific pressure on its corresponding liquid.
The strength of attractive forces is independent of temperature. Higher temperatures with resultant higher kinetic energies make these forces less effective.
Liquid water can exist in equilibrium with water vapor only up to a temperature of 374.1ºC. Later you will learn that neither liquid water nor water vapor can exist at temperatures above 374.1ºC.
Water Alcohol Cooking Oil
At 80° C
355 torr 760 torr 10 torr
At 50° C
92 torr 400 torr 4 torr
At 20° C
20 torr 90 torr 1 torr
What is equilibrium called when liquid molecules enter into the gaseous state? Vaporization
Where does this occur? On the surface of the liquid = evaporation,
throughout liquid = boiling Equilibrium vapor pressure depends on:
a) temperature and pressure b) boiling point of a liquid (the type of liquid)
If a liquid has high intermolecular forces, then what happens to that liquid’s vapor pressure? Why? vapor pressure ↓ high IMFs =
increase hold on the molecules
Boiling. Freezing. Melting
What is boiling? The conversion of a liquid to a vapor, within
the liquid as well as its surface when the equilibrium vapor pressure of the liquid is equal to the atmospheric pressure.
What is the boiling point? The temperature at which the equilibrium
vapor pressure of the liquid is equal to the atmospheric pressure (760 torr).
Boiling happens throughout the liquid…evaporation happens on the surface.
What is the molar heat of vaporization?
The amount of heat energy required to vaporize one mole of liquid at its boiling point.
How does a pressure cooker work? It elevates pressure to raise boiling point and
shorten cooking time.
Freezing and melting
What is the freezing? The physical change of a liquid to a solid.
What is melting? The physical change of a solid to liquid.
What is the molar heat of fusion? The amount of heat energy required to melt
one mole of solid at its melting point.
Are the freezing points and melting points the same temperature?
Yes at 0°C H2O with 6kJ is a liquid
at 0°C H2O without 6kJ is a solid
Chapter 10 Calculations – not in book
Molar heat of Vaporization The amount of heat energy required to
vaporize one mole of liquid at its boiling point. Joules are the standard unit to measure heat
energy. Molar heat of vaporization for water is 40.79
kJ/mole.
2.2 – Heat and Temperature – there is a difference• Heat transfers between objects – flows from hot to cold -
Law of Conservation of Energy • • Ex1:ice cube in a thermos of hot water - ice melts, water
cools - same amount of heat
• SI unit of heat - Joule (J) calorie is also used frequently
• Calorie - the amount of energy required to raise the
temperature of 1 g of water by 1 oC• (Calories – capital letter – really means kilocalories – used
in food energy measurement)
1.000 calorie = 4.184 Joules
Specific Heat Problems• For water, Cp = 1.000 cal/g oC or 4.184 J/g oC for
water • Ex1: How many calories does it take to heat 20. g of
water from 10.0 to 40.0 oC? Also how many J?
• Ex2: How much heat is required to heat 75 g of Iron (Cp = 0.444 J/gCo) from 15.5 to 57.0 oC?
Specific Heat Problems Ex3: What is the specific heat of an object if 250 calories
will heat 55 g of it from 25 to 100.0 oC?
Ex4: - If a 100.0 g sample of silver (Cp = .237 J/g oC) at 80.0 Co loses 50. calories, what will its final temperature be?
Not In Book• NIB: It also takes energy to melt or boil any substance. The amount of
energy required to melt or boil a substance can be expressed by the following equations:
• ΔH = nΔHfusion ΔH = change in energy (J)n = number of moles
• ΔH = nΔHvaporization ΔHfusion = the molar heat of fusion (kJ/mol)
ΔHvaporization = the molar heat of vaporization (kJ/mol)
• ΔHfusion and ΔHfusion are constants and correspond to the amount of energy it takes to freeze (fuse) or boil (vaporize) one mole of a substance.
• When doing heat calculations that involve both a change of state and a change in temperature, make sure the answers for both calculations are written in the same units before adding them together!
Ex1: How much heat energy would be required to vaporize 5.00 moles of H2O
q = ΔHvap·(mol)
= 40.79 kJ/mol · 5.00 mol
= 204 kJ or 204,000 J Ex2: to vaporize 45.0g of H2O
q = ΔHvap·(mol) 45.0g ·1mol
= 40.79 kJ/mol (2.50 mol) 1 18.0g
= 102 kJ or 102,000 J
when....a liquid evaporates, it absorbs energy. Energy is used to overcome attractive forces. The energy doesn’t increase the average energy of the particles, so the temperature doesn’t change.
when...a liquid evaporates, it takes energy from its surroundings that’s why alcohol feels cool to the skin.
it’s also why we get cold when getting out of the shower
Heat of vaporization - Hvap - energy needed to vaporize a unit of substance (mass or moles)
Formula: q = (H vap ) x ( unit ) unit = gram or mole
Ex3 - How much heat does it take to vaporize 50.0 g of water at 100.0 °C
50.0g · 1mol = 2.78 mol
1 18.0g q = (H vap ) x ( unit )
= 40.79 (2.78)
= 113 kJ
Molar Heat of Fusion
The amount of heat energy required to melt one mole of a solid at its melting point.
The molar heat of fusion of water is 6.008 kJ/mole.
Ex1: How much energy would be required to melt 12.75 moles of ice? q = ΔHfus·(mol)
= 6.008 kJ/mol ·(12.75 mol)
= 76.60 kJ
Ex2: to melt 6.48 x 1020 kg of ice?
6.48x1020kg · 1000 g = 6.48x1023 g
1 1kg
6.48x1023 g · 1mol = 3.6x1022 mol
1 18.0g
6.008kJ/mol(3.6x1022 mol) = 2.16x1023 kJ
Heat of Fusion - Hfus = heat of fusion - heat required to change a unit of substance from solid to liquid
same formula: q = (Hfus) x (unit) unit = g or mole
Ex3: - How much ice can be melted by 2.9 x 104 J? 2.9x104J · 1kJ = 29kJ
1 1000J
q = (Hfus) x (mol)
29 kJ = 6.008 kJ/mol x (mol)
= 4.8 mol ice